Makefile: honour $TMPDIR when deciding where to place artefacts.

[tkchia]

No description provided.

[tkchia]

The macOS build on CI seems to be crashing when running the preprocessor (?). Unfortunately I am not very sure how to begin debugging this...

[1184/10055] ACKDIR=/var/folders/g6/rgtlsw6n123b0gt5483s5_cm0000gn/T/ack-build/staging /var/folders/g6/rgtlsw6n123b0gt5483s5_cm0000gn/T/ack-build/staging/bin/ack -mcpm -c.s -o /var/folders/g6/rgtlsw6n123b0gt5483s5_cm0000gn/T/ack-build/obj/mach/proto/fp/s_cpm/adf4/adf4.s mach/proto/fp/adf4.c  -O6 -Imach/i86/libfp 
FAILED: /var/folders/g6/rgtlsw6n123b0gt5483s5_cm0000gn/T/ack-build/obj/mach/proto/fp/s_cpm/adf4/adf4.s 
ACKDIR=/var/folders/g6/rgtlsw6n123b0gt5483s5_cm0000gn/T/ack-build/staging /var/folders/g6/rgtlsw6n123b0gt5483s5_cm0000gn/T/ack-build/staging/bin/ack -mcpm -c.s -o /var/folders/g6/rgtlsw6n123b0gt5483s5_cm0000gn/T/ack-build/obj/mach/proto/fp/s_cpm/adf4/adf4.s mach/proto/fp/adf4.c  -O6 -Imach/i86/libfp 
/var/folders/g6/rgtlsw6n123b0gt5483s5_cm0000gn/T/ack-build/staging/bin/ack: /var/folders/g6/rgtlsw6n123b0gt5483s5_cm0000gn/T/ack-build/staging/lib/ack/cpp.ansi died with signal 11
Pre-processor failed

Thank you!

[davidgiven]

That's great, thanks. Merging.

Re OSX: yes, it's broken, no, I don't know why. It only happens on CI and not on my test machine so my ability to debug it is very limited.

[tkchia]

Thank you @davidgiven ! Maybe I will see if I could find a way to diagnose the cpp.ansi crash.